A WebmasterWorld thread asks how long on average would you guess that it takes Google to find good links and act on it?
Let's assume that this site gives off "good links" when I link to someone. For example, I am going to link to Justilien who suggests in the WebmasterWorld thread that;
For a high-quality link from a site with "a lot of trust" I have seen it affect rankings in as little as a week.
He should see a bump up in some of his rankings in Google on about November 3rd from that link.
I'll be honest, people have told me that soon after I linked to them from within an article on this site, their rankings did improve.
I think it all goes back to trust. You get links from trustworthy sites, you become more trustworthy yourself.
Forum discussion at WebmasterWorld.